Not as it seems
First off, good job on Sol, Riot! He sounds perfect.
Now then onto the theorizing side of this. Sol returning is not a "good" thing at least not for us. Hes been to this world before, probably when he made it, since he is capable of destroying and making anything in the stars above. So whats my point? Well...
He's not here to get rid of the darkness, hes here to get rid of us.
Now here me out, he doesn't hate us but for some one like him it would be much easier to rid of the problem as a whole rather than to deal with it. Why and try to save a planet when he can destroy it and make a new and enhanced one? So what kinda tipped me off that this may be the case?
His voice.
His snobby, stuck up voice. You wouldn't talk like that if you weren't above everything. But clearly he is, by moving a star around what seems to be a planet's surface and then crushing it in his bare hands. Hes grown tired of all this nonsense that Runeterra has made, constantly on the verge of destruction, its either Void this, Harrowing that, yadda yadda yadda.
So know we got a god who can literately just say, " Your annoying" and poof their gone coming to our world. Too "poof" it away. Man, I should of really checked the horoscope huh?
is involved then it would be to stop him, it would be to keep him alive if he is in danger of being destroyed by something or someone. just my guess